Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones (2022)

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5   Work Zone Intrusion Technologies The chapter describes representative technologies that provide the following functionalities to prevent and mitigate the impact of intrusions in work zones: positive protection devices, worker warning systems, and driver warning systems. Each technology in the three catego- ries is discussed in terms of the following aspects: description of the technology, current and potential WZIT applications, effectiveness of the technology, and implementation guidelines. These guidelines serve as general summary guidelines only, and users are encouraged to refer to the referenced literature and manufacturer-provided information for detailed implementation guidelines for the technology under consideration. 3.1 Positive Protection Devices The collection of single units of technology embedded on a large piece of work equipment, such as a truck or mobile trailer, and stand-alone devices that enable high performance safety measures to prevent work zone intrusion before the vehicle intrudes into the work zone is identified in this class of technologies and is labeled as positive protection devices (PPDs). 3.1.1 Autonomous Truck-Mounted Attenuators Technology Description Automated equipment with truck-mounted attenuators are highly automated vehicles that are meant to operate in the work zone without the presence of a human operator. An example is the autonomous truck-mounted attenuator (ATMA) by Kratos Defense, also known as an Autonomous Impact Protection Vehicle (AIPV). An ATMA is a key safety technology that follows behind the leader vehicle, and is an unmanned mobile crash barrier, absorbing the impact of traffic which enters the work zone during slow-moving highway operations such as line painting or sweeping (Kratos, n.d.). Figure 1 shows an ATMA following behind a lead vehicle. Current and Potential WZIT Applications ATMAs have the potential to improve safety during mobile work zone operations by keeping workers out of harm’s way (MnDOT 2021). Workers have a general positive attitude toward this device. This viewpoint is backed by their assumption that it would minimize crash severity by the truck-mounted attenuator itself; it is a reasonable burden connected with the automated technology’s operating procedures; and their overall trust in the technology’s reliability. How- ever, workers expressed reservations about their trust in automation in a variety of situations, including limited vision and during the use of truck-mounted attenuator in higher traffic volumes (Pourfalatoun and Miller 2021). C H A P T E R   3

6 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones Effectiveness The ATMA truck follows the trajectory of a lead vehicle. This concept takes the advantage of linked and automated vehicle technology. The leading vehicle leaves “electronic bread crumbs” for the ATMA to follow, allowing it to function autonomously. A safety driver was present in the ATMA vehicle at all times during a project demonstration. The resulting ATMA testing success- fully functions at speeds of up to 15 mph in day and night work zone situations with a reliable Global Positing System (GPS) signal and the ATMA instructed to follow at distances ranging from 50 to 400 ft. The ATMA has a lidar-based obstacle detection and response system, as well as an extensive internal and exterior human-machine interface to facilitate interactions between system operators and external road users. On straight and curving roads, lateral tracking accu- racy was determined to be quite good. According to the results, longitudinal tracking gives good accuracy (up to 2 meters) at low speeds and ± 22 meters at higher speeds. The majority of the longitudinal error occurs at the start of automation when the lead vehicle is reducing the space between the cars, and the system is constrained by the maximum speed threshold (White et al. 2021). The training document for the operators can be accessed from the following website: https://safed.vtti.vt.edu/wp-content/uploads/2021/06/ATMA-Integration-Plan-8.31.20-1.pdf. Implementation Guidelines An integration plan developed by other researchers offers recommendations for a series of ATMA testing steps prior to usage on live, public roads. The plan specifies the type of test- ing to be performed, objectives to be met, criteria for successful completion, recommended facilities, personnel and staffing recommendations, and an overview of recommended training for management-level stakeholders, ATMA operators, and operational work crew members. The document can be found at: https://safed.vtti.vt.edu/wp-content/uploads/2021/06/ATMA- Integration-Plan-8.31.20-1.pdf. 3.1.2 Mobile Barrier Technology Description A mobile barrier is a mechanical system that serves as a barrier between passing vehicles and the work zone. Mobile barriers are easy to set up and remove in and around short-term work zones during peak traffic hours. Mobile barriers are useful during the daytime and nighttime as some of the barriers have lighting system and a dynamic message sign attached. A crash attenuator may or may not be attached to provide a cushion for the impact of vehicles at the rear end of the Figure 1. Follower ATMA behind lead vehicle. (https://www. workzonesafety.org/files/documents/SWZ/ATMA_project_ background-Kyle.pdf)

Work Zone Intrusion Technologies 7   truck (Mobile Barriers n.d.). Figure 2 shows a mobile barrier being used for a highway work zone operation. Further information can be accessed at: https://www.mobilebarriers.com/. Current and Potential WZIT Applications The use of mobile barriers is recommended where lengthy sections of the work zone and work zone operations are conducted on a daily basis, nightly basis, or when the work zone is reconfigured daily. Mobile barriers are expensive equipment and their size configurations must be accounted for when planning their use in work zones for temporary traffic control. Mobile barriers are effective for short-duration, short-term work zones, moving operations, and incident management. Mobile barriers have been applied in work zone maintenance operations, highway construction work, and for traffic flow management. Mobile barriers are useful for pothole repair, debris pick-up, utility maintenance, crack sealing, relamping, lane marking, drain repair, and median work tasks for work zone maintenance operations. Mobile barriers are also useful for bridge work, including deck and joint repair and inspections, end treatment and gore point repair, slab replacement, guardrail repair, cable replacement, culvert replacement, tunnel work, ITS maintenance, and center lane work tasks in highway construction operations. Last, mobile barriers have been found to be successfully implemented in traffic flow operations and to carry out incident management lane and road closures, full ramp closures, mobile operations, temporary traffic control and re-routing, security protection, spot inspection stations, rolling perimeters, protected areas for critical infrastructure and personnel, and asphalt and pavement pouring tasks (Mobile Barriers MBT Applications n.d.). The additional features that can be added to mobile barriers can be found at the following website: https://www.mobilebarriers.com/. Effectiveness This device’s mobility provides for quick work zone setup and removal, allowing managers to cut project time and expense, schedule around peak traffic hours, and reduce roadway congestion. Project managers can also reduce work zone footprints and boost worker personnel efficiency by using integrated equipment and supplies (Mobile Barriers MBT Applications n.d.). The cost of mobile barrier trailers is generally high compared to other technologies with prices in the hundreds of thousands of dollars. Implementation Guidelines The traffic face of the mobile barriers must be flush with the edge of the adjacent travel lane, and channelizing devices should be placed at the required spacing from the end of the Figure 2. Mobile barrier protecting workers in highway work zone. (https://ops.fhwa.dot.gov/ publications/fhwahop17043/fhwahop17043.pdf)

8 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones taper in advance of the designated work area along the appropriate longitudinal line with the barrier. The mobile barrier may replace the advanced warning vehicle when the work area is on the shoulder or the shadow vehicle when the work area is in the travel way. The mobile barrier may also replace the shadow vehicle located in the lane where the work is occurring. The mobile barrier may not be placed in a closed lane between two open lanes. The non-barrier side should be adjacent to a closed lane(s), shoulder, or median (Mobile Barriers MBT Applications 2021). Apart from the implementation guidelines in work zones, critical decisive factors such as cost and time should be considered when deploying mobile barriers per the work zone project specifications and requirements. Mobile barriers can be used when there is need for positive protection for exposed work hazards or during night work (with appropriate lighting), and can be used when there is limited time as it relates to work hour restrictions, setup and removal, productivity, work area access, transportation routes, and removal and storage of the device. When using a mobile barrier in a tunnel or on a bridge, limited escape areas can present safety hazards. These guidelines are based on suggestions by the manufacturer and the guidelines presented in the Manual on Uniform Traffic Control Devices (MUTCD) (MUTCD Drawings & Guidance n.d.). 3.1.3 Automated Flagger Assistance Device Technology Description An automated flagger assistance device (AFAD) is a mobile unit with signal lights or stop/slow signs to alert vehicles to stop or proceed and a mechanical gate system that provides an alert to drivers. Audio systems, while not a standard feature, can be installed to provide audio feedback in case a vehicle moves forward during a stop sign. The entire operation is a mechanically operated temporary traffic control device set up around work zones and is operated automatically with the programmed setup for the duration of stops and movements (ATSSA 2020). Current and Potential WZIT Applications Two types of AFADs are recognized for use in work zones and should follow the standard guidelines as per Part 6E of the MUTCD. The first type utilizes a remotely controlled stop/slow sign paddle mounted on a trailer, and the second type uses a red/yellow lens with a mechani- cally operated gated arm. Figure 3 shows the two types of AFADs. State transportation agencies Figure 3. AFAD systems: red/yellow lens type (left) and slow/stop paddle sign (right) (ATSSA 2020).

Work Zone Intrusion Technologies 9   recognize the potential benefits of AFADs and impose and expand the device standards and guidelines more than what is set by the MUTCD. In some cases, additional countermeasures are added in, such as warning lights, backup battery power, and flashing lights or gate arms on the slow/stop signs. The steps and guidance summarized in the AFAD implementation guide- lines section are suitable for appropriate environmental and physical work zone configurations (ATSSA 2020). Effectiveness AFADs are easy for the drivers to see and spot sooner from a distance as they are larger than a human flagger and have a mechanical gate arm. The easy spotting of the AFAD allows drivers to gain more reaction time. Some AFADs have built-in intrusion alarms that are automatically set off when a vehicle crosses a pneumatic tube laid out in the work zone or the vehicle hits the AFAD itself. During the alarm, the AFAD may begin flashing visual lights. The use of an AFAD removes the likelihood of a human operator facing the traffic flow and removes the human operator to a safe, remote location (IntelliStrobe 2020). Implementation Guidelines AFADs are generally suited for short-term or intermediate-term lane or road closures, such as for bridge maintenance, haul road crossings, guardrail repair, and pavement patching. AFADs can be used for daytime or nighttime operations and, if used during the night, the AFAD must be illuminated as per section 6E.08 of the MUTCD. An AFAD is typically placed within the shoulder of the road. All AFAD applications should abide by the specific standards set forth in the MUTCD section 6E.04 and satisfy the crash worthiness standards based on the device weight. Detailed specifications for slow/stop AFADs are available in section 6E.05 of the MUTCD, and in section 6E.06 of the MUTCD for the red/yellow AFADs (ATSSA 2020). More information can be found at: https://www.workzonesafety.org/files/documents/training/fhwa_wz_grant/ atssa_afad.pdf. In one research study, the AFAD was found to be useful as drivers, when nearing a work zone, stopped 44.7 ft farther away from the AFAD as opposed to a human flagger. Drivers also began to brake 58.2 ft earlier when facing an AFAD (Brown et al. 2018). In another study, 93% of participants completely understood the red/yellow lens style AFAD if it had a gate arm and stopped a far distance from the AFAD (Finley et al. 2011). 3.2 Networked Systems for Workers Technologies that directly support the safety of workers through various devices connected to a central communication system or stand-alone system unit and are placed on work zone channelizing devices or worn by the workers as a personal wearable safety device are included in the Networked System for Workers class. 3.2.1 Intrusion Alert Systems with Equipment-Mounted Sensors Technology Description This category of intrusion alert systems contains equipment-mounted sensors that utilize a single technology or multiple technologies such as radar (scanned radar), high-precision differential GPS system, accelerometers, gyroscopes, and magnetometers, for position and orientation sensing to detect vehicle intrusions.

10 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones An illustrative example of such a system is a radar-based system that can identify a potential work zone intrusion from several vehicles while also warning the errant driver and jobsite personnel who may be in danger. This is called the AWARE system (https://theasphaltpro.com/ articles/oldcastle-aware-system/) and it consists of a sensor that includes electronically scanned radar, high-precision differential GPS, accelerometers, gyroscopes, and magnetometers for position and orientation sensing. To monitor traffic in the area, high-definition video and multiple wireless interfaces are used. When an intrusion is detected, a warning is sent out to the workers and motorist (Asphalt Contractor 2016). Current and Potential WZIT Applications Systems such as AWARE can monitor potential work zone intrusions and notify workers in the work zone. AWARE itself is currently in the development stage and will not be commercially accessible until the manufacturer conducts additional field tests. The system is one of only two with a personal safety device for individual workers (the other system is Traffic Guard), and it is suggested for long-term highway construction zone projects (Marks et al. 2017). The main components of the AWARE system are Raven (Radar Sensor), Worktrax (GPS based alert unit), visible and audible threat deterrent unit, and base station (mobile app accessible). Consider- ations for the use of this system also include due knowledge of the detection regions as specified by the manufacturer. Effectiveness Texas Transportation Institute (TTI) evaluated the AWARE system for the manufacturer. In a lane closure, AWARE activates warning lights and an auditory alarm, flagging, and tangent alignment. A lane closure was observed during a right curve alignment and left curve align- ment. When the system is tilted, the activation distances differ; the distance in the right curve is greater than the distance in the left curve. The device tested had a detection range of 500 ft and the body alarm reliably produced vibratory and audio notifications at a range of 300 ft during testing that could provide additional warning cues and increase time for workers to take evasive actions (Theiss et al. 2017). Despite the potential benefits of these technologies, their effective- ness is adversely affected by issues relating to false positive alarms, inadequate warning audio levels, etc. These factors must be taken into consideration before implementing this class of technologies. Implementation Guidelines AWARE is useful in work zone operations longer than one day duration, mobile work zone operations, and a taper longer than or equal to 1,500 sq. ft (Marks 2017). The first version is for a lane incursion system capable of detecting work zone invasions, and the second version is the Sentry, which is primarily intended for use by flaggers. The Sentry version is made up of two parts: a sensor/alarm housing unit with a Raven radar sensor, light-emitting diodes (LEDs), an alarm speaker, and personal alarms called Worktrax. Figure 4 depicts these devices on a roller. Each Sentry comes with four Worktrax units. Worktrax alarms should be tied to a worker’s arm or carried in their pockets. Based on the speed of the predicted intrusion vehicle, AWARE generates three unique types of alerts. The first form of alarm is exclusively produced as the Worktrax receives alerts when the stopping sight distance (SSD) determined is 6 seconds. The second alarm activates the Sentry’s LED warning lights when the SSD determined is 4.5 seconds. The third alert is activated primarily to advise the drivers, and produces a loud siren if the driver fails to correct the approach speed. If the driver fails to correct the travel path, Worktrax and the Sentry generate alarms (Mishra et al. 2021).

Work Zone Intrusion Technologies 11   3.2.2 Intrusion Alert Systems with Cone/Barrel-Mounted Sensors Technology Description Intrusion alert systems with cone/barrel-mounted sensors use sensors embedded in the devices and generally are impact-activated work zone intrusion devices. The intrusion devices are mounted on a cone/barrel and generally are activated when a vehicle hits the cone/barrel during the intrusion impact. An illustrative example is SonoBlaster, a system that emits an audible alert sound that is activated when the cone/barrel attached to the SonoBlaster is impacted or struck by a vehicle. The SonoBlaster consists of a CO2 cartridge and alarm unit. When the SonoBlaster is struck, the punctured CO2 escapes from the cartridge and emits an air horn sound. This device can be mounted on traffic cones, drums, delineators, frames, and other types of barricades. Current and Potential WZIT Applications Such systems are useful for detecting intrusions into the work zone after the intrusion has occurred. There also is potential for the use of such systems with other technologies like smart- watches and wearables to provide more personalized warnings to workers. Effectiveness It was noted that the cumulative response rate through three SonoBlaster tests were 92% and 85% at 50 and 100 ft, respectively. As observed through the installation and activation pro- cesses, results proved to provide technology evaluation as “easy to use.” In another scenario, the SonoBlaster was rendered useless as it was run over by a vehicle and the CO2 cartridge was punctured without sounding the alarm. In other narrow work zone sites, the SonoBlasters were knocked over and false positives were recorded as vehicles passed by close to the device in the narrow work zone. Implementation Guidelines A worker should follow the installation steps to set up the device. First, the mounting bracket should be installed at the base of the cone. Second, the SonoBlaster is cocked using a keychain tool. Third, the unit is placed in the work zone in “safe” mode. Last, the control knob is rotated from “safe” to “ready” mode, and the unit is active and ready to use. Figure 5 shows the final Figure 4. Operation demonstration of the AWARE (Ullman and Theiss 2019).

12 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones setup look of the SonoBlaster. The SonoBlaster is activated when there is impact-tilt contact by a vehicle and the device emits an audible alarm sound in the work zone at an audio level of 125 decibels for 15 seconds. The SonoBlaster CO2 cartridge is deemed a one-time-use only (Traffic Worker Alert System n.d.). 3.2.3 Intrusion Alert Systems with Networked Cone or Barrel System with Sensors Technology Description This class of technologies refers to systems in which channelizing devices like cones and barrels are equipped with sensors and wireless technologies to detect intrusions and provide warnings to workers. The Intellicone system, a portable site alarm (PSA) powered by motion sensitive and communications-based technologies, is an example of such a system. The device utilizes General Packet Radio Service/Global System for Mobile (GPRS/GSM) communications and GPS sensors. The Intellicone system serves as a communications-mediator between the system units in the field and central command center. The system also includes a Traffic Management Unit, Intellicone Unipart Dorman (flashing lights unit), and a Sentry Beam (vehicle sensor) ranging up to 3 ft. The system devices can be mounted on a traffic cone or channelizer using bolts. The electronic system can be mounted on cones that transmits the signals when impacted by a vehicle, producing auditory and visual alarm in the work zone. Figure 6 shows the system in place for a simulated work zone and Figure 7 shows a close-up view of the devices themselves. Current and Potential WZIT Applications Such systems add the capability of wireless communications on work zones to the sensing capabilities of individual sensors mounted on cones and barrels. These connections are par- ticularly useful in longer work zones and noisy environments where it is necessary to provide warnings in closer proximity to workers. There is also potential for the use of such systems with other technologies like smartwatches and wearables to provide more personalized warnings to workers. Effectiveness The Intellicone system is effective in providing an alert to workers. In some instances, like all cone or barrel-mounted devices, the system suffers from a prevalence of false positive alarms Figure 5. SonoBlaster devices (left) and their mounting on a cone (right).

Work Zone Intrusion Technologies 13   due to the possibility of sideswiping by vehicles that knock over cones and barrels without resulting in intrusions. Implementation Guidelines In addition to guidelines provided for the other cone or barrel-mounted systems, line of sight to ensure radio communication must be considered for this type of device. 3.2.4 Intrusion Alert Systems with Pneumatic Tubes Technology Description Pneumatic WZIT systems utilize pneumatic tubes connected to a transmitter, and the tube activates its alert mechanisms, such as an alarm siren or a strobe light. The tubes are placed parallel to the road shoulder at the entry point to the work zone. The alert mechanisms are activated when a vehicle passes over the pneumatic tube. An example is the Worker Alert System (WAS), an auditory and visual alarm system designed and developed to be wirelessly triggered when a vehicle crosses over a positioned pneumatic tube in a work zone. The pneumatic tube has a pressurized sensor that enables the trigger to a portable case alarm up to 100 ft when a vehicle crosses over the tube. The auditory and visual alarms are found to be activated for about 6 seconds. Figure 8 shows the components of the WAS system. Figure 6. Test setup of Intellicone technology on a closed course roadway. (https://www.frontiersin.org/articles/10.3389/fbuil.2019.00021/full) Figure 7. Radio-based alarm and impact sensors.

14 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones Current and Potential WZIT Applications WAS is activated when a vehicle passes over the trip tube. The pressure sensor sends a signal wirelessly to the portable alarm case (PAC) and personal safety devices (PSDs) ranging up to 1,000 ft away. The PAC triggers the audible alarm and flashing light, alerting everyone nearby in the work zone at an audio level of 68 decibels (Traffic Worker Alert System n.d.). Employee exposure when laying out the pneumatic tubes for the WAS is a drawback. In addition, the limited length of the pneumatic tube is an issue, and the vendor must be contacted to get the pneumatic tube of a specific length for long freeway closures. Another drawback was that work- ers needed to be in close vicinity to the WAS components in order to be conscious about the vehicle intrusion and attain sufficient reaction time to save themselves from a vehicle intrusion (Mishra et al. 2021). Effectiveness It is noted that the WAS technology’s strengths are its ease of use and the effectiveness of the triggering mechanism. The cost and effectiveness of the device’s alarm, on the other hand, were cited as disadvantages of implementing the WAS technology. WAS is distinguished by the presence of an audible and vibratory (haptic) alarm generated by the PSD that personnel can carry in their pockets. The vibration can be felt if the device is wrapped around one’s arm or is in one’s pocket. Implementation Guidelines WAS installation is done manually by the operator by laying out a pneumatic tube transverse to the flow of traffic by following these steps. First, the trip tube is deployed across the lane and the tube pressure sensor box is powered up through pressing a button. Second, the PAC is attached to a piece of infrastructure inside the work zone. Third, the workers turn on their PSDs and verify the green LED is visible. Last, the pneumatic tube is stepped on to trigger the alarm and test the system for its operability (Traffic Worker Alert System n.d.). 3.2.5 Intrusion Alert Systems with Bluetooth Technology Description This type of WZIT system contains a network of Bluetooth zones that act as an intrusion alert system. Several devices utilize the Bluetooth low-energy (BLE) based proximity sensing and alert system, which uses adaptive signal processing (ASP) methods to communicate between Figure 8. WAS components (Nnaji et al. 2020).

Work Zone Intrusion Technologies 15   the Bluetooth zones. This application not only extends to detect close proximity sensing, but the automated collection of information enables sharing e-notices to drivers and diverting traffic flow (Park et al. 2016). Current and Potential WZIT Applications The results of field evaluations indicate that the WorkzoneAlert app is reliable for detecting BLE beacon signals at an average distance of 127 m from traffic signs or portable radar speed signs, and successfully announces the corresponding message associated with each BLE beacon (Liao 2019). Effectiveness In a series of experiments, the Bluetooth technology proved to be a reliable and appropriate alarm system with minor performance differences. The alert display function was positively validated at a real-time construction site and performance results showed a positive response by the participating equipment operators and on-site work zone workers (Marks et al. 2017). Implementation Guidelines The range of Bluetooth devices for communication, along with their battery life, must be considered when deciding to utilize these systems in work zones. Further development work is needed to provide more implementation guidance. 3.2.6 Intrusion Detection with Computer Vision and Ranging Technology Description This class of technologies utilizes computer vision and ranging with the use of cameras, Internet of Things (IoT), and LiDAR to provide real-time auditory or visual feedback to workers in the work zone. The computer vision and ranging generally utilizes artificial intelligence and machine learning to continuously learn about the environment, keep track of the objects within the range, learn about the physical attributes, assess the danger or threat, and provide real-time feedback to the user. An example is SmartCone, which houses these features that enable the early warning system through detection by high-level technology that is safe and easy to use. The warnings are sent out early on and provide mission-critical feedback to people in the area and any personnel who need to be notified. Current and Potential WZIT Applications Such systems can provide several advantages over other sensor systems due to the use of a camera that can cover a wide area for monitoring. Because there is no contact with infrastructure, it is much easier to place and remove these sensors; this advantage can lead to easier maintenance of the system. Effectiveness This system has not been widely used yet, and further experimentation is required to evaluate its effectiveness. Implementation Guidelines Considerations for implementation include the occurrence of occlusions of the camera sensor that can negatively impact performance. The placement of sensors is also important to ensure that sufficient reaction time is accounted for.

16 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones 3.2.7 Smartwatches/Bracelets Technology Description Smartwatches are electronic watches with the capability to connect to a wireless system through Bluetooth and Wi-Fi systems and enable the user to read messages and get alerts or warnings through flashing lights or vibration. An application of the smartwatch integrated with a network of Bluetooth zones was seen in a long-term work zone configuration. The vehicles were equipped with a Bluetooth signal emitter chip where there were Bluetooth receiver chips along the work zone boundary. When the Bluetooth emitter-enabled vehicle came close to the receiving Bluetooth zones, a message alert and a vibration was sent to workers wearing the smartwatches. This communication enabled a timely alert of a threat as well as a head start for the workers to respond in the situation. Current and Potential WZIT Applications The potential applications of smartwatches to communicate warnings to workers in con- junction with other systems are immense. However, these implementations are still under research and development. Effectiveness Smartwatches can prove to be an effective means of communicating warnings to workers. However, further experimentation is required at this stage. Implementation Guidelines Despite widespread prevalence of smartwatches for personal use, their widespread implemen- tation on work zones is still evolving. Important considerations would be to ensure adequate battery life and connectivity, and to ensure that workers are not distracted by other applications on their devices. 3.3 Driver Warning Systems Technologies that are attentive toward the vehicle drivers and provide early forms of notifica- tion about an upcoming work zone in the upstream location are grouped together within the driver warning systems category and are presented in the following sections. 3.3.1 Work Zone Speed Warning with Dynamic Message Signs Technology Description Dynamic message signs (DMSs) have been employed in highway work zones in the United State as an innovative temporary traffic control (TTC) device for many years. Their develop- ment has proven to be effective in decreasing mean vehicle speed before the work zone. Speed reductions are achieved through numerous changes in the message, such as a graphical images or sequential messages displayed instead of a text-based message, radar attached to the message sign that allows notifying the drivers of their speeds, and a change in the rate of flashes per minute to socially influence the vehicle drivers. Figure 9 shows a DMS displaying information about upcoming traffic conditions. Current and Potential WZIT Applications It has been noted that text DMS, graphic-aided DMS, and graphic DMS can have the following effects on work zones: (1) their use resulted in a mean vehicle speed reduction of 13%, 10%, and 17%, respectively; (2) using a graphic-aided DMS reduced mean vehicle speed more effectively

Work Zone Intrusion Technologies 17   than using a text DMS from 1,475 ft to 1,000 ft upstream of a work zone; and (3) using a graphic DMS reduced mean vehicle speed more effectively than using a text portable changeable mes- sage sign (PCMS) (Bai et al. 2011). The DMSs broadcasts notifications informing the drivers of the upcoming work zone. Effectiveness Certain case studies on the use of DMS have indicated average speed reductions of more than 3 mph as well as improved traffic flow in a bridge work zone (Edara et al. 2011). Rear-end collisions are one of the leading causes of work zone incidents (Meng and Weng 2011) that could be mitigated through the use of more effective signage systems that provide advance warning for motorists. Despite their advantages, some limitations are their susceptibility to being hacked and losing their connection to the traffic information relay system. These limitations can signifi- cantly and adversely affect traffic flow by causing congestion, increased travel time, and broad- casting unreliable information to motorists (Ermagun et al. 2021). Other reasons attributed to work zone incidents (decade 1990 to 2000) are not obeying safety regulations and rules, and road decreasing in width prior to work zone where the effect of DMS is nullified (Dingus et al. 1998; Bryden and Andrew 2000). Implementation Guidelines According to analysis and lessons learned from the case study validation, DMS performance evaluation is primarily dependent on three factors: the environment of the DMS application, i.e., urban or rural freeway corridor; the availability of data required for evaluation; and the limitation of resources available for evaluation, i.e., time and/or manpower. The application area, whether urban or rural, determines the potential benefits of either delay reduction (improved mobility) or crash reduction (safety). The availability of data, before and after the DMS application, allows or limits the scope of review. Furthermore, most accountable agencies’ resources are always restricted (Mounce et al. 2007). 3.3.2 Queue Warning Systems with Networked Cone/Barrel System Technology Description Queue warning systems (QWSs) alert vehicle drivers to an impending traffic queue by trans- mitting electronic messages to portable changeable message signs and providing a warning to Figure 9. Dynamic message sign displaying information of upcoming traffic ahead. (https://tti.tamu.edu/wp/wp-content/uploads/2013/12/v49n4highway-workzone-lg.jpg)

18 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones vehicle drivers at the upstream location of the construction zone. Another feature is that it alerts vehicle drivers to slow down owing to traffic ahead or to take a detour to save time before reaching the starting location of the traffic queue. When networked with a cone/barrel-mounted WZIT device, the system could be used for work zone intrusion prevention and mitigation. Current and Potential WZIT Applications A QWS is recommended for use on long-term interstate roadway projects where stopping sight distances are not adequate for drivers to observe the formation of queues near work zones. Examples of such instances include work zones located in roadway sections containing curved horizontal alignments and changing vertical alignments. Effectiveness A DOT that has used this system previously experienced high levels of accuracy when setup factors such as the location and alignment of devices were optimal. Use of QWS was noted to be a labor-intensive process and training for the contractors was important. The performance of the QWS was validated through field observations, available data and travel time data. The QWS fared well in all aspects and functioned as expected. The QWS was seen to be functional for 90% of the observed time. Implementation Guidelines Constant attention toward the device conditions and alignment is recommended during implementation. It was observed that sometimes drivers did not slow down during the curved section of the road even though they saw a message displayed on the DMS. The QWS cannot be implemented in work zones around bridges due to limited space and other physical limitations. 3.3.3 Unmanned Aerial System for Signage Technology Description An unmanned aerial system (UAS) is a completely mechanical aircraft system consisting of three system components: (1) an autonomous or human-operated control system that is usually on the ground or a ship, but may be on another airborne platform; (2) an unmanned aerial vehicle (UAV); and (3) a command and control (C2) system, which sometimes is referred to as a communication, command, and control (C3) system to communicate with the remote user. UAVs and a camera system provide real-time traffic monitoring with high temporal and spatial resolution that helps to dynamically manage the work zone by interacting real-time with changeable message boards, driver mobile phones, a traffic management center, and law enforce- ment agency. Current and Potential WZIT Applications The potential applications of a UAS are immense for preventing work zone intrusions; it can serve as a queueing monitoring system, intrusion alert system, and errant vehicle warning system without need for sensors on the roadway. However, this technology is relatively new and these applications have not been proven yet. Effectiveness Barlow et al. (2020) noted that the UAS proved to successfully decrease mean vehicle speed by 1.25 mph during UAS-based drone TTC operations. Further experimentation is needed to prove the effectiveness of this technology.

Work Zone Intrusion Technologies 19   Implementation Guidelines Special training and permits are required for the operator with adequate contingencies put in place to handle the power requirements of drones and their operations near highways. 3.3.4 Connected and Autonomous Vehicles (CAVs) Technology Description Connected vehicles are generally operated with a dedicated short-range communications (DSRC) system from the user to the vehicle through a fixed wavelength to provide in-vehicle information for the drivers. Connected vehicles prove to be effective in improving traffic flow and to reduce congestion on freeways caused by work zones. In-vehicle information includes, but is not limited to, providing warnings of upcoming variable speed limits, queues ahead, lane closure, and vehicle-to-vehicle messages. Autonomous vehicles (AV) are self-driven vehicles powered (absent a human driver) through technologies such as Global Navigation Satellite System (GNSS) systems, sensory systems, and radar systems, and have built-in Bluetooth, gyroscope, and mechanical systems. As roadway work zone construction is a dynamic environ- ment that does not always have the same pre-defined activities, the challenge lies in the move- ment of AV through the work zone. AVs generally operate on artificial intelligence systems and machine learning systems where the environment is continuously monitored, and complex actions are executed simultaneously to run the vehicle. AV has found its application in the work zone through special pavement markings. The special pavement markings are constantly interpreted by the systems and allow the vehicle to be driven within the speed limit set around the work zone. Current and Potential WZIT Applications While such technologies are not directly created for work zones, they have the potential to significantly make work zones safer by eliminating human distractions, communicating work zone instructions to incoming vehicles, and enabling the receipt of multiple sources of electronic data from the work zone to improve safety. Effectiveness In-vehicle information for CAV includes, but is not limited to, providing warnings of upcoming variable speed limits, queues ahead, lane closures, and V2V messages. Connected vehicles can provide real-time feedback through messages displayed on variable message signs communicated via road sensors (UMass Transportation Center 2019). The applications extended to improving driver response, where it was observed that 20 professional drivers were seen to reduce vehicle speed when a notification regarding adverse weather conditions given to the driver, and a smooth braking response was recorded around work zones within a driving simulator environment (Raddaoui et al. 2020). Implementation Guidelines Because these vehicles are owned and operated by motorists, implementation guidelines are not generally applicable in this case. 3.3.5 Wearable Lighting Technology Description Wearable lighting consists of wearable devices worn by workers typically during nighttime operations. Generally, the high visibility garments that are a standard practice for workers is

20 Guide to Alternative Technologies for Preventing and Mitigating Vehicle Intrusions into Highway Work Zones augmented by a strobe light wrapped around the hardhat and powered by a battery strapped to the worker. The lights flash around to indicate to the driver of the vehicle of the presence of the worker in the night. Products such as the Halo Light are worn on the top of the hardhat to ensure sufficient lighting is visible to the driver and to ensure detection of the worker. Current and Potential WZIT Applications According to the findings of a recent study (Gambatese and Jafarnejad 2018), increased temporary roadway lighting makes workers more visible to motorists and equipment operators, resulting in somewhat higher vehicle speeds. There is a concern about visibility, and it is advised that extra temporary roadway lighting be installed. Personal, wearable lights are also recom- mended for workers who are not near large equipment or other light sources (Gambatese and Jafarnejad 2018). Studies show that the impact of the Halo Light on visibility of the worker is minimal when the worker is close to standard work zone lighting (e.g., light tower and balloon light); the light from the Halo Light is washed out by the bright surrounding lights and there- fore less effective. In the absence of the balloon light and portable lights, the impact of the Halo Light on worker visibility increased. Small wearable lighting systems (e.g., neon arm and head bands) are also recommended, since they improve visibility and identification when the wearer is moving (Nnaji et al. 2020). Effectiveness Adverse weather conditions contribute toward the severity of work zone crashes in cases under dark conditions with no lighting. In such instances, the conditions reduce visibility while the driver is vulnerable to upcoming obstacles; this situation reduces the time frame for the driver to respond. Another instance observed is when forced and late merging is observed at taper areas, the severity of crash increases when a large heavy vehicle, such as a truck, compels hard- braking and the vehicle either swerves or skids to intrude in the work zone area (Raddaoui et al., 2020). Nighttime paving typically benefits from traffic free congestion, but leads to poor visibility that poses a risk to the driver and workers. This situation is helped with the presence of a Halo Light (Nnaji, Jafarnejad, and Gambatese 2020). Implementation The primary consideration for the use of wearable lighting is to ensure proper care of the device and ensure that the batteries are charged after use and prior to subsequent use.